Catalytic conversion of hydrocarbons



July 28, 1942. L. s. KASSEL CTALYTIC CONVERSION OF HYDROCARBONS FiledFeb. 13, 1959 CONDEN SER 4 FRACTIONATOR www;

REACTOR l2 HEAVIER UIL lNvg-:NTQR

LOUIS S. KASSEL FURNACE 8 REAcToR |22- HEAVIER UIL FuRNAcE e ATTORNEYPatented July 28, 1942 CATALYTIC CONVERSION 0F HYDRO- CARBONE muis s.Kassel, chicago, nl.. assigner tu Universal Oil Products Company,Chicago, lll., a corporation of Delaware Application February 13, 1939,Serial No. 256,023

6 laims. (Cl. 196-52) The invention relates specifically to an improvedmethod of operation in processes involvingl simultaneously conductedendothermic and exothermic reactions; the endothermic reaction involvingthe formation and deposition of heavy carbonaceous material such'as cokeon a mass of contact material, such as a bed of catalyst, disposed inthe zone of endothermic reaction, and the exothermic reaction involvingthe oxidation ci previously deposited carbonaceous material from a bedof catalyst or contact mass in a separate reaction zone, heat beingsupplied from the exothermlc to the endothermic reaction. The purpose ofthe invention is to regulate the quantity of carbonaceous materialdeposited in the endothermic reaction zone so as to approximatelybalance the heat generated by its subsequent oxidation in the exothermicreaction zone with the heat requirements of the endothermic reaction.This is accomplished by controlling the quantity of relatively highcoke-forming components in the reactants supplied to the endothermicreaction zone.

The invention is particularly advantageous as applied to processes forthe catalytic cracking of hydrocarbon oils and the subsequent moredetailed description of the invention, as applied to catalytic cracking.will serve to illustrate its features and advantages. The invention may,however, be employed to advantage in any process of the general typeabove mentioned, including dehydrogenation, aromatization, isomerizationand the like, wherein coke or other carbonaceous material is depositedon a catalyst or contact mass and periodically burned away to renew thecontact surface and restore catalytic activity.

Catalytic cracking processes, in common with other processes oi thegeneral type above re-v ferred to, are of three general classes in sofar as the features of the invention are concerned. The rst classconsists of processes in which the hydrocarbons to be treated are passedonly once through the zone of endothermic reaction and the resultingproducts separated and recovered. The second class consists of processeswherein insufciently converted intermediate products resulting frominitial conversion of the raw charging stock are recycled to the samezone of endothermic reaction Whereto the charging stock or a selectedportion thereof is supplied. 'Ihe third class consists of processes inwhich insufficiently converted'intermediate products resulting frominitial conversion lof the raw charging stock are supplied to andfurther converted in a separate zone of endothermic reaction. For thesake of simplicity, the first class will be subsequently referred to asa once through type of operation, the second class as a recycle"operation and the third class as a "selective" type of operation, theseterms being now rather commonly accepted and understood in the industry.

The invention is applicable to each of the three general classes ofprocesses above outlined. As applied to the once through type ofoperation, the objects and advantages ofthe invention are obtained bycommingling regulated minor amounts of relatively heavy, highcoke-forming hydrocarbons, formed within the system or derived from anexternal source, with the relatively clean charging stock of lowercoke-forming character- .istics supplied to the reaction zone when morecoke deposition is required in this zone. As applied to a recycleoperation, the invention provides for increasing the quantity of coke orcarbonaceous material deposited on the contact mass in the reactionzone, when needed, by increasing the quantity of relatively heavycomponents included in the intermediate conversion products yrecycled tothe reaction zone and decreasing the relative proportion of highcoke-forming components in the recycle stock when less coke depo sitionis desired, this being accomplished by varying the quantity of heavyresidual product removed from the system. This variation is reflected inthe quality of the residual product with respect to the quantity ofrelatively light residual fractions included therein and is ac.complished by varying the operating conditions' employed in that zone ofthe system wherein the residual product recovered is separated from thelower boiling conversion products. A combination of the two methodsabove outlined may be employed in the selective type of operation,regulated quantities of relatively heavy, high cokeforming materialbeing commingled `with the relatively light, clean charging stocksupplied to one reaction zone, when more coke deposition is requiredtherein, and the quantity and quality of the residual product beingvaried to control the relative proportion of high coke-forming materialin the intermediate fractions supplied to the other reaction zone. i

The invention also contemplates an alternative but non-equivalent methodof operation which may be employed to vadvantage when it is desir-.-7able to recover a residual product of'uniform, good quality. Inaccordance with this alternative method of operation. which isapplicable to any of the threeclasses of systems above men- 'tioned,regulated minor mounts of the residual liquid product are blended withthe raw charging stock or with -the intermediate conversion products orwith-,the mixture of intermediate conversion products and chargingstock, as the case may be. n

In processes of the general type above referred to, the quantity of heatevolved in the exothermic phase of the system is ordinarily of suchmagnitude that its efficient recovery is a matter of economic necessity.It is common practice to utilize the same for generating steam in awaste heat boiler but the steam thus generated is usually more thansufllcient to satisfy the requirements of the process and, except inspecial cases where the excess steam can be otherwise usefully employed,a heat recovery system oi' this type is not feasible. On the other hand,considerable heat is ordinarily required at a relatively hightemperaturelevel to carry on the processing step or endothermic `phaseof the reaction and it is decidedly advantageous, in most instances, totransfer the heat generated in the exothermic phase of the system to theendothermic phase. However, the two Vphases are ordinarily not inthermal balance and it is still necessary for best economy to recoverthe excess heat generated in the exothermic phase or, in case there is adeficiency in the heat generated, to supply additional heat to 'theendothermic phase. In either case, a rather complicated and expensivesystem is required. When the endothermic and exothermic phases of the.system are maintained in substantial thermal balance, as provided bythe invention, the initial cost of the installation, as well as theexpense of operating the same, is considerably reduced and the reducedcost will, in many instances, constitute the difference between acommercially successful process and an economic failure.

It should be understood that in referring to a substantial thermalbalance between the endothermic and exothermic phases of the system, Irefer to the reactions simultaneously taking .place in the reactionzones containing the contact mass or catalytic material rather than tothe overall heat requirements of the process, since the inventioncontemplates external cooling and heating means in other portions of thesystem, the object of the invention being to balance the heat evolved inthe reaction zone wherein the catalyst or contact mass is beingrevivified with that required in the reaction zone containing the activecatalytic material or contact mass, towhich reactants are ordinarilysupplied in preheated state and wherefrom the reaction products areordinarily discharged to separating, condensing and collectingequipment.

Each reaction zone is alternately employed for conducting theendothermic and exothermic reactions, said reactions taking placesimultaneously in separate zones. Preferably, heat is transferred fromthe zone of exothermic reaction to the zone of endothermic reactionthrough a relatively static heat transfer medium such as a bath ofmolten metal, molten salt or the like or directly from themetallic'walls of one reactor to the other or, when desired, hotcombustion gases generated by burning of the carbonaceous materialduring the exothermic reaction may be passed in contact with a mass ofhigh heat capacity material such as rebrick or the like wherein it isstored and subsequently liberated toV the endothermic reaction. Suchrelatively simple forms of reactors cannot be employed with success inprocesses of the type described, except when the endothermic andexothermic phases of the process are in substantial thermal balance.Otherwise a more complicated system involving the use of a circulatedheating and cooling medium with provision for supplying external heat orextracting excess heat from the same between the exothermic andendothermic reactions is required.

The accompanying drawing diagrammatically illustrates a catalyticcracking apparatus in which the process of the invention may beconducted and, in conjunction with the following description, will serveto more clearly illustrate the features oi' the invention and variousalternative modes of operation which it provides.

Referring to the drawing, hydrocarbon oil charging stock for the processwhich is preferably a relatively clean distillate such as gas oil,naphtha or the like, susceptible to substantially complete vaporization,is supplied through line i and valve 2 to pump l wherefrom it isdirected through line l and may be supplied, all or in part, throughvalve 5 in this line and line t to Vheating coil 1 wherein it preferablyis substantially completely.vaporized and heated to a temperature atwhichY the desired cracking reaction will take place upon conta-ct ofthe heated vapors with the catalyst employed. Heat is supplied to coil 1from furnace B and, preferably, to assist vaporization and repressthermal cracking in coil 1, regulated quantities of relatively lowmolecular weight material such as steam or normally gaseous hydrocarbonsare commingled with the materials supplied to the heating coil, line land valve Il communicating with line l being provided for this purpose.

That hot vaporous hydrocarbons and low molecular weight materialcommingled therewith are directed from coil 1 through line il to reactori2 which, in the case here illustrated, contains a plurality ofelongated fluid passageways il, each substantially filled with a bed ofsuitable granular catalytic material capable of promoting the crackingreaction. As indicated in the drawing, the fluid passageways I3 areconnected with suitable manifolds il, I6, I6 and I1 by branch lines insuch a manner that fluid passageways I3 form two separate reactionzones, in one of which the endothermic cracking reaction is taking placewhile the catalyst in the other reaction zone is being reviviiled byburning therein carbonaceous materials deposited during a previouscracking reaction in this zone. Heated reactants from coil 1 may besupplied from line Il through valve i8 in manifold I4 to one of thereaction zones, while oxygen-containing gases for revivifying thecatalyst are supplied from line Il through valve .2li in manifold Il tothe other reaction zone.

After a predetermined period of operation, during which carbonaceousmaterial is deposited on the catalyst in the reaction zone whereincatalytic. cracking is taking place and during which the catalyst in theother reaction zone is restored to a high degree of catalytic activityby burning the carbonaceous material therefrom, the reaction zones areswitched with respect to the endothermic and exothermic reactions byclosing valve Il and directing the heated reactants through valve 2| andmanifold IB into the reactor containing the reviviiied catalyst and byclosing valve 20 and directing the revivlfying gases through valve 22and manifold I4 into the reactor containing the catalyst which nowrequires revivification.

vWhen reviviiication of the catalyst ie taking place in the reactionzone communicating with manifold Il, spent 'revivifying gases l aredischarged therefrom through valve 23 and line 24. When revivificationis taking place in the reaction zone communicating with manifold I1,spent revivifying gases are dischargedj therefrom through valve 2E andline 24. When cracking is taking place in the reactionzone'communicating with manifold it, the resulting hot conversionproducts are directed therefrom through .valve 28 and line 2l toseparating chamber 28. When catalytic cracking is taking place in thereaction zone communicating with manifold i7, resultant lhot conversionproducts lare directed therefrom to valve 28 and line 2l to separatingchamber 2d.

Reactor i2, in the particular case here illustrated, comprises a nest ofmetallic sections 86, cach containing one ora plurality of the fluidpassageways i3 and so arrangedthat heat is transferred directly throughthe metallic walls of the several sections from the zone of exothermicreaction to the zone of endothermic reaction, whereby the heat requiredfor conducting the endothermic reaction is supplied by the exothermicreaction. Although not indicated in the drawing, reactor i2 ispreferably well insulated to conserve heat, It will be apparent that anyother specific form of reactor, wherein efficient heat transfer from theexothermic to the endothermic zone lis obtained, may be employed Within.the scope of the invention and, except for this qualification, theinvention is not limited to the type of reactor or reactors employed.However. full advantage of the benefits to be derived from the featuresof the invention can best be obtained by employing one of the relativelysimple and inexpensive forms of reactors which the present inventionmakes acceptable and satisfactory, but which will not permit emcientoperation when the endothermic and exothermic reactions are not insubstantial thermal balance. Some of the other forms which may besuccessfully employed to advantage have been previously mentioned. Theyinclude the sc-called regenerative type and the type employing a bath ofmolten metal, salt or the like which acts as the heat transfer medium aswell as the type illustrated which employs metal-to-metal contactbetween the walls of the endothermic and exothermic zones.

The stream of hot conversion products passing from the reactor tochamber 28 is preferably cooled to a temperature below that of activethermal cracking and at which the desired septity and characteristics ofthe residual product thus controlled to suit requirements. Additionalcooling may be provided, when required, in chamber 28 by supplyingregulated quantities of a suitable cooling oil such as charging stock,intermediate liquid conversion products or the like to the upper portionof the chamber through line 3B and valve 31, suitable fractionating orcontacting means oi any wellknown form, not illustrated, being providedin the upper portion of chamber 28, when desired.

In the case-here illustrated, the upper portion of the same column,within which separating chamber 2B is disposed, 'comprises fractlonator38 and the components of the conversion products which are not includedin the residual liquid product separated in chamber 28 are supplied invaporous state from chamber 28 to fractionator 38 wherein their heavycomponents which boil above the range of the desired final lightdistillate product, such as gasoline, are condensed to form refluxcondensate comprising the intermediate liquid conversion products .ofthe process which are withdrawn from the lower portion of thefractionator through line 39 and may be removed, all or in part, fromthe system to cooling and storage, or elsewhere, through valve 40 inline 39 or may be returned, as will be later described, via coil 1 toreactor l2 for further cracking treatment in this zone in commingledstate with the charging stock, or they may be directed to separatecatalytic cracking treatment, as will be later described.

eration of their residual liquid and vaporous constituents is assistedin chamber 2B. This may be accomplished by commingling a suitablecooling oil with the products'passing through line 2. When recycleoperation is employed, all or a regulated portion of the charging stockmay be employed as cooling oil in line 2l by directing the same theretofrom line i through line 3i and valve 82. In addition to. or instead ofemploying charging stock for this purpose, intermediate liquidconversion products formed within the system, as later described, may,when desired, be supplied to line 2 through line 33 and valve 3d.Preferably, a superatmospheric pressure is employed in the endothermicreaction zone and by control of valve 35 in line 2l, in conjunction withthe cooling employed in line 21 and/or chamber 28, the desiredseparation of vapors and residual liquid is effected in the latter zoneand the quan- Fractionated vapors of the desired end-boiling point,comprising normally gaseous materials and fractions of the conversionproducts boiling within the range of the desired gasoline, are directedfrom the upper portion of fractionator 38 through line 4l and valve 52to condenser 43 wherefrom the resulting distillate passes together withuncondensed and undissolved gases through line M and valve 45 tocollection and separation in receiver 46. The uncondensed andundissolved gases vare released from the receiver through line t1 andvalve 48 and the distillate collected in this zone is removed therefromto storage or to any desired further treatment through line 45 and valve50. When desired, regulated quantities of the distillate collected inreceiver d6 may be returned by Well known means, not illustrated, to theupper portion of fractionator 38 to serve as a cooling and reiiuxingmedium in this zone.

The drawing illustrates an apparatus in which the once-through, recycleor selective cracking type of operation may be accomplished. Any ofthese lthree types may be selected to suit requirements and they will bediscussed separately in the subsequent description of the drawing.

When once-through operation is employed, the intermediate liquidconversion products condensed from vapors formed in fractionator 38 areremoved from the system through line 39 and valve lill. Sin-ce a lightcharging stock is preferably employed ln this type of operation, theamount of coke deposited on the catalyst in reactor i2 will ordinarilybe insufficient to'satisfy the heat requirements of the crackingoperation in this zone and to increase the coke deposition' employed forthis purpose and line 5|, controlled by valve 52, is provided forsupplying the same through line 8 to coil 1 with the charging stockwhich, in this type of Operation, is supplied directly to coil 1, aspreviously described.

The invention also contemplates the use of regulated quantities of theresidual liquid conversion products separated from the vapors in chamber28 as the coke-forming material. When this mode of' operation isemployed, residual liquid withdrawn from the lower portion of chamber 28through line 58 is directedthrough valve 54 in this line to pump andsupplied therefrom in regulated quantities through line 58, line 51,valve 58 and line 6 to heating coil'1, together with the charging stockwhich is also supplied to line 8, as previously described, from pump 3.That portion of the residual liquid from chamber 28 not supplied, asdescribed, to coil 1 is removed from the system through line B5 andvalve 68 to cooling and storage or elsewhere, as desired.

When recycle operation is employed, all or a regulated portion of thereflux condensate formed in fractionator 38 is directed from line 38through line 58 and valve 6D to pump 6I wherefrom it is supplied throughline 62, line 63, valve 6I and line 6 to coil 1. In this type ofoperation the charging-stock may be either a relatively lowboilingdistillate or an oil of relatively wide boiling range and, dependingupon its characteristics, may be supplied directly to coil 1 throughline l, valve 5`and line 8 or directed from line 4 through line 3|,valve 32 and line 21 into chamber 28. The latter flow is employed incase the charging stock contains a quantity of high-boiling componentsin excess of that required to give the desired coke deposition inreactor l2. Any such excess of high-boiling components in the chargingstock, as well as the excess of high-boiling components in theconversion products discharged from reactor i2, are included with theresidual liquid removed from chamber 28 by regulating the temperatureand pressure conditions employed therein. the remaining components ofthe charging stock and of the conversion products which boil above therange of the overhead product from fractionator 38 being condensed inthis zone as reflux condensate and supplied therefrom, as previouslydescribed, to coil 1.

It will be apparent that, when the last described method of operation isemployed, the

residual liquid removed from chamber 28 may.

in some instances, be robbed of desirable lowboiling fractions (whichare included as highboiling components in the reflux condensate formedin fractionator 38) to such an extent that the residual liquid productis of an inferior quality. When this condition would arise, I preferablyemploy an alternative method of operation in which conditions are soregulated in chamber 28 as to produce a good quality residual liquidproduct and, to compensate for the deflclency of high coke-formingcomponents in the cracking stock, regulated minor amounts of the wholeresidual liquid product are returned by a line 53, valve 54. pump 55,line 58, line 51, valve 58 and line 6 to heating coil 1, the remainingquantity of residual liquid being removed from the system to cooling andstorage or elsewhere, as desired, through line 65 and valve 68.

When the selective type of cracking operation is utilized, a separateheating coil 1', furnace 8 and reactor I2' are provided, as indicated inthe drawing. for separate treatment of the reflux condensate fromfractionator 88. This separate cracking equipment may be of the samegeneral form, but not necessarily the sar'ne size as the desiredcorresponding equipment in which the charging stock is treated. Theinvention is not limited to the same general type of equipment in thetwo `cracking steps but, to simplify the present description, the samegeneral type of equipment is illustrated for each of the cracking stepsin the drawing. The reference numbers designating the different portionsof the equipment employed in the charging stock cracking step areduplicated by corresponding prime numbers. indicating correspondingportions, in the reflux cracking step. The functions of thecorresponding portions of the equipment are the same and the foregoingdescription of their functions and operations, as applied to thecharging stock cacking step, also apply to the reflux cracking s ep.

With the selective cracking operation, reflux condensate fromfractionator 88 is supplied by means of pump 6I through line 82, line68', valve 84' and line 8' to coil 1', steam or other light molecularweight material such as hydrocarbon gases being admitted to line 8',when desired, through line 8 and valve I0'. With this type of operation,the charging stock is preferably a light oil which is supplied directlyto coil 1 in the manner previously described. When, due to thedesirability of producing a good quality liquid residue. the refluxcondensate supplied to coil 1' does not contain a sufficient quantity ofhigh coke-forming constituents, regulated minor quantities of theresidual liquid product may be supplied from pump 55 through line 56,line 51', valve 58 and line 6 to coil 1 or a suitable relatively heavyhigh coke-forming oil from an external source may be supplied inregulated uantities to line 8' through line 5l' and valve The conversionproducts discharged from reactor I 2 are directed through line 21', line21 and valve 85 to chamber 28 whereby they are separated into thevaporous and residual liquid components in this zone. together with theconversion products from reactor I2.

While the invention is not limited to the use of any specific crackingcatalyst, it should be one which will satisfactorily withstandtemperatures during reviviflcation within the range or somewhat higherthan those suitable for accomplishing the catalytic cracking reaction,in order that heat for the latter may be supplied directly to thereaction zone wherein catalytic cracking is taking place from thereaction zone wherein the catalyst is being revivified, the temperaturedifference in these two zones being sufficient to effect good heattransfer therebetween. So long as the temperature level at which thecatalyst may be successfully revivifled is sufficiently high, thetemperature level prevailing in the zone wherein catalytic cracking istaking place may be regulated to suit requirements, since thetemperature in the revivifying zone may be controlled to suitrequirements by regulating the relative proportions of'l oxygen andinert materials in the revivifying gases and by controlling the rate offlow of the revivifying gases through the catalyst bed being revivifled.One specific catalyst which possesses a high degree of activity andmeets the requirements of withstanding fairly high reviviflcationtemperatures comprises a silica-alumina mixture from which alkali metalions are substantially ellminiated during its preparation to preventfusing during reviviflcation. This catalyst may advantageously containminor amounts of other materials such as, for example, zirconia whichwill retard shrinkage of the catalyst particles during reviviiication athigh temperatures.

When employingV a catalyst such as above mentioned, and a relativelylight charging stock such as gas oil, the catalytic cracking reaction ispreferably conducted at a temperature of the order of 900 to 1100 F.,preferably with a gauge pressure oi' the order oi 10 to 50 pounds, ormore, per square inch with a suil'icient quantity oi steam or other lowmolecular weight material present to materially reduce the eiiectivepressure, preferably to approximately atmospheric.

In general, parainns can be catalytically crackedtc produce high yieldsof gasoline with less coke deposition than oils containing a highproportion oi' olenns and/or aromatica but conditions within the rangeabove given may be selected for any of the three types of cil mentionedas well as mixtures thereoi1 and for the type of operation employed.

Preferably, the cracking stock is supplied to the catalytic reactionzone at a temperature of the order of 875 to 950 F., or thereabouts, andthe heat supplied to this zone from the exothermic phase of the systemis sumcient to maintain the desired temperature in the catalyticcracking zone.

'I'he pressure employed in separating chamber 28 may be varied fromsubstantially the same as' that employed in the catalytic cracking zonedown to substantially atmospheric pressure, depending upon the desiredsplit-up between residual liquid and intermediate liquid conversionproducts. Controlled cooling of the conversion products prior to theirintroduction into chamber 28 and Within that zone will also assist incontrolling the characteristics oi the residual liq` uid product and theintermediate liquid conversion products. Normally,` the conversionproducts are cooled prior to their introduction into chamber 28 to atemperature of the order of 600 to 800 F., or thereabouts, dependingupon the pressure employed in chamber 28 and the cooling accomplishedwithin this zone. The temperature of the vapors entering fractionator 88will range, for example, from 500 to 750 F., or thereabouts, dependingupon the pressure employed and the amount of heavy high vcoke-formingfractions which it is desired to include in the reflux condensate formedin this zone. 'The quantity oi residual liquid recovered from the systemmay vary from 2 to 20%, or thereabouts, based on the raw oil chargingstock, depending upon the operating conditions employed and the desiredcharacteristics ci the intermediate liquid products with respect to thequantity of high cokeforming components included therein and upon thequantity of residual liquid returned to the catalytic cracking zone. Y Y

As an example of one specific operation of the process, conducted in anapparatus such as illustrated and above described, employing as chargingstock a straight run paraiiinic gas oil of about 34 A. P. I. gravity,the charging stock is ccmmingled-with a small amount of residual liquid,comprising a portion of the residual liquid product removed from chamber28, and with approximately 100 mol per cent of steam. The mixture isheated in coil 1 to an outlet temperature of approximately 910 F. with agauge pressure at this point in the system of approximately 75 poundsper square inch and is supplied at approximately this temperature andpressure to reactor i2 wherein it is passed alternately through the tworeaction zones in contactwitl' active catalyst, while the catalyst inalternate reaction zones is being reviviiied. The reviviiying gasescomprise combustion gases containing approximately 3% oi air and aresupplied to .the reactor at a 'temperature of approximately 900 F. Thecatalyst employed comprises catalyst granules or pellets ofsubstantially uniform size and shape containing approximately 89.5%alumina, approximately 3% silica and approximately 7.5% of zirconia. Thequantity of catalyst employed amounts to approximately 0.33 cubic footper cubic foot of hydrocarbon (measured as' liquid) contacted with thecatalyst per hour and the volume of reviviiying gases employed amountsto approximately 2000 cubic reet, per cubic icct oi catalyst, per hour.Approximately minute periods of cracking and reviviiication are employedin each reaction zone. The conversion products leave reactor i2 at atemperature of approximately 950 F. and a superatmospheric pressure ofabout 18 poundsper square inch. Substantially the same press'ure isemployed in chamber 28 and conversion productsv are cooled prior totheir` introduction into this zone to a temperature of approximately 675F. by commingling therewith regulated quantities of the redux condensateformed in fractionator 88 after the latter has been cooled to atemperature of approximately 400 F. Approximately 5% of residual liquid,based on the charging stock, is removed from chamber 28, approximately3% of this material being recovered and approximately 2% being recycledto heating coil 7. 'Ihe pressure in fractionator 88 is substantiallyequalized withl that employed in chamber 28. l'ihe reilux condensateformed in iractionator 88 hasy a boiling range of approximately 400 to700 F. and contains approximately 75% of material boiling froml 400 to600 F. and approximately 10% of material boiling above 650 F. Reiiuxcondensate is supplied, together with approximately 100 mol percent ofsteam to heating coil l' wherein it is heated to an outlet temperatureof approximately 930 F. at a gauge pressure of about 75 pounds persquare inch. The vapor steam mixture enters reactor l2 at approximatelythis temperature and pressure and the operation oi reactor l2 is similarto that above outlined forreactor I2. The conversion products leavereactor I2 at a temperature of approximately 975' F., are commingledwith the conversion products in reactor l2, reduced to a temperature' ofabout 675 F., as above described, and introduced into chamber 2B.

The above described operation will yield per barrel of charging stock,approximately 80% oi 400 F. end-point gasoline having an octane numberof approximately 82 as determined by the motor method and approximately15% of gases containing a high concentration oi readily polymerizableoleflns. The residual product comprises a satisfactory fuel oil and, asabove indicated, amounts to approximately 3% of the charging stock.

I claim as my invention:

1. In a process wherein endothermic and exothermic reactions aresimultaneously conducted, the endothermic reaction involving theformation and deposition of heavy carbonaceous material, such as coke,on a contact mass through which a stream of hydrocarbon reactants ispassed and the exothermic reaction involving the oxidation, from asimilarmass of contact material, of such carbonacecus material deposited6 y asoman.

thereon during a prior endothermic reaction. and heat being transferredfrom the exothermic to the endothermic reaction, the improvement whichcomprises increasing the amount of such carbonaceous material depositedon the contact mass in the endothermic phase of the system, so as tomaintain the exothermic and endothermic reactions substantially inthermal balance, by adding relatively heavy, high coke-formingoonstituents. to said'stream or hydrocarbon reactants. s

2. 'The process denned in claim 1, further characterized in that saidstream of hydrocarbon reactants consists 'essentially of relativelylow-boiling hydrocarbons which are supplied to the zone of endothermicreaction lin heated substantially vaporous state and to which regulatedminor quantities oi' higher`boiling hydrocarbons are added to increasecarboniormatlon and deposition on the contact mass during saidendothermic reaction.

8. The process denned in claim 1, further characterized in that saidstream of hydrocarbon reactants comprises a mixture oi low-boilinghydrocarbons from an external source and intermediate liquid conversionproducts formed within the system, said mixt'ure being supplied to thezone ot endothermic reaction in heated substantially vaporous state andthe composition of said intermediate liquid products. with respect totheir heavy. high coke-forming constituents, being controlled by varyingthe quantity of residual liquid fractions separated from the vaporousconversion products prior to their fractionation tor the formation ofsaid intermediate liquid fractions.

4. The process defined in claim 1, further characterized in that saidstream of hydrocarbon reactants comprises a mixture of low-cokeiorminghydrocarbons from an external source and low-coke-iorming intermediateliquid conversion products formed within the system, regulated minorquantities of residual liquid conversion products formed within thesystem being added to asid mixture to increase the amount of carbonformation and deposition in the zone oi' said endothermic reaction.

5. In the catalytic cracking f hydrocarbon distillates of relatively lowcoke-forming tendency, wherein carbonaceous matter is deposited on thecatalyst during the endothermic cracking reaction, while simultaneouslyoxidizing from a separate mass of the catalyst carbonaceous matterdeposited thereon during a prior cracking reaction, and heat istransferred from the exothermic oxidizing reaction to the endothermiccracking reaction, the improvement which comprises adding to thedistillate to be cracked an oil of higher coke-forming tendency than thedistillate in an amount such as to maintain the exothermic andendothermic reactions substantially in thermal balance.

8. In the catalytic treatment of hydrocarbons wherein carbonaceousmatter is deposited on the catalyst during an endothermic reaction ofthe hydrocarbons, while simultaneously oxidizing from a separate body ofthe catalyst carbonaceous matter deposited thereon during a priorendothermic reaction of the hydrocarbons, and heat is transferred fromthe exothermic oxidizing reaction to the endothermic hydrocarbonreaction, said hydrocarbons being too low in coke-forming tendency todeposit on the catalyst during the endothermic reaction sumcientcarbonaceous matter to supply, on oxidation thereof, the heatrequirements of the endothermic reaction, the improvement whichcomprises adding to the hydrocarbons. prior to the catalytic treatmentthereof, hydrocarbons of higher coke-forming tendency in an amount suchas to maintain the exothermic and endothermic reactions substantially inthermal balance.

LOUIS S. KASSEL.

